Electric sockets are located at many places in houses, farms, stores, offices, factories, etc. so that various electric powered devices such as vacuum cleaners, milkers, display lamps, business machines, power tools, etc. can be plugged into the sockets and powered with electricity.
The universal problem encountered by the users is that when the end of the cord is inadvertantly reached in the use of an electric powered device, when someone tries to walk through the cord, and/or when the plug fits loosely in the socket, for examples, the plug comes out of the socket and the powered devices loose their source of power.
Users have tied or looped the cord around pipes, projections, etc. at the socket to prevent the plug from coming out as an almost universal practice. This tends to break the wire in the cord and it also foreshortens the length of the cord leaving reduced working extension.
Plug retainers of the prior art have not been very satisfactory as they entail mounting the retainer and dismounting the retainer with the securing screw each time a plug is inserted and extracted. This also entails remounting the shield on the sockets each time the screw is removed. Because of the unhandiness of these retainers, they have not found much success in being adopted in general use where plugs are not permanently inserted in the sockets. For the more usual temporary mounting, they have not been used in any significant numbers.